1. De Franchis M., “Un teorema sulle involuzioni irrazionali,” Rend. Circ. Mat. Palermo, 36, 368 (1913).
2. Howard A. and Sommese A. J., “On the theorem of de Franchis,” Ann. Sc. Norm. Super. Pisa, Cl. Sci., IV Ser., 10, No. 4, 429–436 (1983).
3. Alzati A. and Pirola G. P., “Some remarks on the de Franchis theorem,” Ann. Univ. Ferrara Sez. VII (N. S.), 36, 45–52 (1990).
4. Tanabe M., “On rigidity of holomorphic maps of Riemann surfaces,” Osaka J. Math., 33, 485–496 (1996).
5. Tanabe M., “A bound for the theorem of de Franchis,” Proc. Amer. Math. Soc., 127, 2289–2295 (1999).